Investigation of the Wettability and the Heat Transfer on Laser-Manufactured Complex Surfaces during Vapour Condensation at Saturated and Superheated Condition

该项目的主要任务是通过激光制造技术系统地和有选择地修改过冷基板的表面质量，从而实现蒸汽冷凝过程中散热的显著改善。应该指出的是，与未改性的表面相比，在相同的操作条件下实现了散热的增加。在拟议的研究项目的框架中，它打算使用一个光滑的，非结构化的参考表面以及几个由铝和铜制成的微结构表面。关于接触角增大，除了应用激光制造技术之外，表面还经受电化学处理。通过这一步骤，在表面上实现纳米结构化，从而降低表面能，增大液体-壁边界处的接触角，最终实现强化传热。通过实验，确定影响因素（接触角/滞后、表面粗糙度、操作压力等），这可能会显着影响整个冷凝过程，将被识别的时间和空间上的高分辨率测量热传递和表面润湿和它们的相互依存关系相对于地形变化将被显示。此外，纳米-微米结构对传热的贡献以及润湿特性应该通过使用测量值进行数学建模，并且应该用现有的文献和实验数据进行验证。

The main task in this project is to systematically and selectively modify the surface quality of sub-cooled substrates by means of laser manufacturing technology, such that a significant improvement in heat dissipation during steam condensation is achieved. It should be noted that, compared with non-modified surfaces, the increase in heat dissipation is achieved at equivalent operating conditions.In the frame of the proposed research project it is intended to use a smooth, unstructured reference surface as well as several microstructured surfaces made of aluminum and copper. With regard to the contact angle enlargement, the surfaces are subjected to an electrochemical treatment in addition to the application of the laser manufacturing technique. Through this step, a nanostructuring is to be achieved on the surfaces, which should lead to reduced surface energy and larger contact angles at the liquid-wall boundary, in order finally to achieve an intensification of the heat transfer.From the experiments, determining influencing factors (contact angle / hysteresis, surface roughness, operating pressure, etc.), which can significantly influence the entire condensation process, will be identified by temporally and spatially high-resolved measurements on heat transfer and surface wetting and their interdependencies with respect to topography changes will be shown. Furthermore, the contribution of nano-micro-structures on heat transfer together with the wetting characteristics should be modelled mathematically by using of measured values and should be validated with the available literature and experimental data.